It is well known in the art that situations arise where it is important to qualitatively or quantitatively determine the presence and concentration of oxidants in a patient's urine. As will be appreciated, accurately detecting the presence of heavy or abnormal concentrations of oxidizing agents in the urine of a patient can help the diagnosis of a patient's condition and appropriate treatment. For example, abnormally high concentrations of oxidizing agents in urine can result from diarrhea in children and other oxidative stress and clinical conditions requiring proper diagnosis and medical attention.
In addition to medical diagnosis, accurately determining, qualitatively or quantitatively, the presence of abnormal concentrations of oxidants in urine is important in other situations. Take drug screening for example. In certain instances and professions, individuals may be required to undergo testing for illegal or banned substances. Although there are very accurate means and methods of determining if an individual has consumed or is under the influence of banned substances, these methods are prohibitively expensive for the random screening of individuals in most instances. Typically, a less-costly alternative is to have an individual provide a urine sample that will be tested for the presence of illegal or banned substances, or more accurately, the metabolites of these substances.
With drug testing, it is customary to perform an inexpensive, initial screening test on a urine sample. If there is a positive result, then the sample can be re-tested with a different method or another sample taken and sent for further testing. This two-step procedure avoids the expense of conclusively evaluating every sample with expensive testing procedures because only the samples that test positive during screening need more rigorous examination for the presence of drugs. Accordingly, individuals who fear that their urine will be positive for the presence of banned substances in the initial test may try to mask the substances or otherwise prevent their detection.
In the past, individuals would try to switch samples or substitute a clean sample for their own. Also, individuals would try to dilute the sample in vitro so that the concentration of the substances resident in the urine would fall below the threshold for detection. These methods of avoiding detection during the testing process are easily prevented by having the individuals monitored while giving a sample (and insuring no water sources are available during the process). Under these conditions, some individuals would try to dilute the sample in vivo. To successfully dilute a sample in vivo, the individual must drink massive quantities of fluids to artificially increase the water content of their urine. To detect and thus prevent this kind of tampering with a sample, urine specimens are routinely analyzed for baseline physiological parameters known to be present in the urine of healthy individuals. For example, specimens are assayed for creatinine concentration and specific gravity, to determine whether the sample has been diluted in vivo.
Adulteration of a urine sample poses unique problems in detecting tampering. “Adulteration” refers to the addition of chemicals to a urine sample to mask the presence of the drug or to interfere with the drug-screening method's ability to detect the drug. A number of readily available commercial products have been used as adulterants. In essence, any product that includes an oxidizing chemical, such as bleach, nitrite, chromate, iodates, or peroxidase, may be effective in preventing a positive reading during the drug screening process. As will be appreciated, some oxidizing agents are effective in destroying 11-nor-delta-9-THC-9-carboxylic acid (THC-acid) and morphine when added to urine samples. Alternatively, these agents can be used to cause conflicting test results by interfering with the immunoassay reagents (as opposed to the drug constituent of the sample) needed to detect the presence of the drugs metabolites.
For example, it has been reported that chromate, nitrite, permanganate, periodate, persulfate, hydrogen peroxide/ferrous ammonium sulfate, and oxone (DuPont product) at a concentration of 10 mmol/L destroy THC-acid almost completely within 48 hours at room temperature. Sodium oxychloride at 50 mmol/L also has similar effects on THC-acid. Moreover, peroxidase from food sources in combination with hydrogen peroxide may effectively destroy THC-acid in a urine sample. Finally, in addition to the masking effect of oxidizing agents, some of these agents also interfere with the GC-MS confirmation procedures typically employed in drug testing, thereby preventing conclusive results.
In an effort to combat adulteration, some prior artisans recommend testing for an adulterant; especially when it appears that a substances is interfering with the drug testing procedures. For example, a procedure for detecting nitrite by diazotizing sulfanilamide and coupling the product with N-(1-naphthyl)ethylenediamine and chromate by 1,5-diphenylcarbazide is in place in many drug-testing laboratories. Alternatively, nitrite can be detected by high-performance ion chromatography and capillary ion electrophoresis. However, both of these procedures suffer from many drawbacks, including exorbitant wastes of time, expense, equipment, and reagents, not to mention the inability of these methods to detect other oxidizing substances.
A qualitative iodide-iodine color test has been proposed for detecting some oxidants. However this test suffers from the severe disadvantage of not having a characteristic absorption spectra in 400-700 nm to permit quantitative analysis.
As will be appreciated, there are countless oxidizing agents that could interfere with the drug-testing procedures or results. Unfortunately, the testing of a urine sample for the presence of each and every oxidant by a procedure unique for each specific oxidant is prohibitively difficult and expensive.
The foregoing underscores some of the problems associated with drug testing. Furthermore, the foregoing highlights the long-felt, yet unresolved need in the art for reliable methods and means for detecting adulterated urine samples. The foregoing also highlights the long-felt, yet unresolved need in the art for reliable methods and means for screening patients to detect abnormal oxidant concentration for diagnosing and treating patients.